Sunflower seed-specific HSFA9 as a chromatin memory inducer before the seedling transition

Resumen de la comunicación oral presentada en el 14th ISSS biennal conference "Challenges Seed science in a changing world" from 3 to 7 july 2023 París

HSFA9 (A9) is a seed-specific transcription factor that contributes to embryonic desiccation tolerance and seed longevity in sunflowers. A9 also links the regulation of seed maturation with that of early seedling greening through its e↵ects on various light receptors. Transcriptomic analyses of transgenic tobacco seeds suggested that A9 might affect chromatin remodeling. Here, using formaldehyde-assisted isolation of regulatory elements (FAIRE) and Micrococcal Nuclease digestion, we analyzed the A9 e↵ects on chromatin accessibility in three developmentally relevant genes shortly after seed imbibition. Comparison between di↵erent pairs of transgenic and sibling non-transgenic lines revealed that A9, expressed from a seed-specific promoter, enhanced chromatin accessibility at proximal promoter regions in all analyzed genes, two of which are direct A9 targets. Furthermore, a memory e↵ect was observed, as the induced chromatin accessibility persisted for up to four days after seed imbibition, when A9 was no longer detected. A9-induced chromatin effects involved labile/unstable nucleosomes placed at proximal promoter locations where A9 induced total or partial nucleosomal eviction. Specific inhibitors of Brahma-like ATPase subunits of SWI/SNF, chromatin remodeling, complexes and histone deacetylase (HDAC) impaired A9- induced memory. The results of this study suggest that A9 is a master epigenetic regulator that functions during the transition from seed to seedling. By inducing a memory ffect, A9 can help facilitate, speed, and synchronize the early greening of seedlings and their stress tolerance. This could lead to improved seedling establishment and enhanced crop productivity. Additionally, this study highlights the importance of SWI/SNF-remodeling and HDAC activity for A9-induced memory.

Peer reviewed